How do I update old blender projects to the newest version of blender?
You don't need to update your .blend file.
You just need to open them with a newer version of blender.
Uninstall older version of blender and install new one (you can also install a new version without uninstalling the older one).
Start new blender version (to open the newer version of blender go to the folder where you installed it and launch it), then open your blend file from the blender software.